Known in the art is a compression ignition type internal combustion engine designed to ignite main injection fuel by premixed charge compression ignition, wherein main fuel is injected at a relatively early timing of the compression stroke and auxiliary fuel is injected around when a cool flame reaction of the main fuel starts, so as to thereby lower the temperature of the premixed charge of the main fuel by latent heat of vaporization of the auxiliary fuel and delay the timing of transition from, the cool flame reaction to hot flame reaction of the main fuel, that is, the ignition timing of the main fuel (for example, see Japanese Patent Publication No. 2004-3439A).
In this compression ignition type internal combustion engine, the ignition timing of the main fuel is controlled to the target ignition timing by controlling the amount of auxiliary fuel.